The present invention relates to improvements in a rotary screen printing machine, particularly for textile printing to permit the proper alignment of the screens for registration of the colors to be printed with minimum expense and time.
It is now well-known in the textile industry to print patterns on fabrics using rotary screens. These are typically cylindrical screens having formed in them a plurality of holes corresponding with the locations in which a print paste color is to be extruded onto fabric. The screens are mounted in a sequence along a printing machine, over top of a belt on which the fabric travels at a rate of speed corresponding to the circumferential rotation speed of the screens. Thus, as the screens rotate and print paste is extruded through the holes of the screens, the fabric passing underneath on the blanket receives the print paste.
In order to print multi-colored patterns, the print paste extruded through the various screens must be applied to the fabric in a careful manner, so that the print paste applies to the portion of the fabric intended. That is, the patterns printed by the different screens must be "in registration", or "in fit" to prevent undesired overlapping of print paste or leaving uncolored gaps between print paste.
As can be appreciated, the printing machines are adapted to receive a multiplicity of different screens and print pastes so the different colorways, patterns and pattern repeats can be accommodated on a given machine. Each time one of these is to be changed, the screens from a previous patterns job are removed and replaced with screens for a new print job corresponding with the new pattern to be printed. In such a changeover, the exact mounting of the screens on the drive heads of the print machine can vary somewhat, particularly if a new style is being installed. The practice heretofore has been to use trial-and-error to advance and retard the various screens to cause them to come into fit, while a waste fabric known as a leader cloth is passed through and receives the print paste. Often, extensive amounts of such cloth must be wasted as well as loss of print paste and operator time involved in making the fine adjustments necessary to bring the different colors into registration. Despite long use of machines of this type and the long-felt desire to permit textile operators to avoid these costs in pattern changeovers, the need persists for an apparatus and method to minimize the expenses involved in such changeovers.